Laserfiche WebLink
CLEARWATER <br /> G R O U P, I N C <br /> • Envi rn n men tuf Sr ry i res <br /> sampling (February, 1995) The majority of this contamination was present in the vadose zone It <br /> is likely that, due to processes of biodegredation and volatilization, only a fraction of this original <br /> mass remains Residual volume calculations are presented in Attachment 3 <br /> The volume of soil impacted by water movement through the capillary fringe is considered to be <br /> negligible <br /> Water <br /> Based on the results of water sample analyses presented over the term of the investigation at this <br /> site, it is estimated that very little, if any, gasoline is present in water beneath this site Results of <br /> lab analyses of water samples collected over the course of this project indicate that, while gasoline <br /> contamination appears to have been present in the early stages of site characterization, <br /> concentrations steadily declined following removal of the source of impact (the former USTs) It <br /> is noted that groundwater has risen from 25 to approximately lb feet bgs over this same time <br /> frame, examination of tabulated lab data, however, does not show a strong correlation between <br /> • water depth and contaminant concentration It is likely that the observed decline in concentration is <br /> more closely associated with natural occurrences - dispersion, volatilization and biodegredation <br /> Conclusions <br /> Based on the results of investigation to date it is apparent that only a small volume of hydrocarbon <br /> contamination (no more than 11 gallons of gasoline) remains in the soil at the referenced facility <br /> As noted in presented text, it is evident that the vast majority of the source materials were removed <br /> following UST closure and soil excavation It has been demonstrated that the residual <br /> contamination has no impact on overall water quality in the vicinity of the areas investigated It has <br /> been further demonstrated that water beneath the property to the east (Southland) is free of <br /> contamination emanating from the subject site Testing conducted by Southland has confirmed the <br /> presence of a significant release of hydrocarbons from the tank system at the 7-11 site <br /> Given the results of the remedial and investigative work completed to date, it is clear that no <br /> additional benefit can be gained through continued activity It is therefore recommended that the <br /> existing monitoring wells be abandoned and the file formally closed by the San Joaquin County <br /> 4 <br />